Since liquid crystal itself does not emit light, in various liquid crystal display (hereinafter referred to as “LCD”) devices such as liquid crystal display and liquid crystal television, external light sources are required to implement display. The light emitting diode (hereinafter referred to as “LED”) backlight has become the mainstream backlight at present as it has the advantages of good coloring characteristics, long service life, mercury free and environmental protection, and the like.
LED backlight can be divided into two types: a side-edge type LED backlight and a direct type LED backlight according to the distribution position of LED. The side-edge type LED backlight is widely used in LCDs with middle and small sizes due to its advantages of less LEDs required, low cost and thinness. FIG. 1 illustrates a partial sectional view of side-edge type LED backlight, which includes a backboard 1, a light guide plate 2 and an optical film 3, as well as backlight LED structures 10 located at two sides of the light guide plate 2 (only one side is shown in FIG. 1), and further includes a glue frame 4 for fixing the backlight, and a display panel 6 is arranged above the backlight. Wherein, as shown in FIG. 3, the backlight LED structure 10 includes an LED bracket 20 and an LED chip 7 fixed on the LED bracket 20. The backlight LED structures 10 are fixed at two sides of the light guide plate 2 through a lamp strip 30 with a certain fitting gap guaranteed.
However, at present, bright spots or bright lines appearing at two sides of the display panel 6 are bad phenomenon frequently occurring in side-edge type LED backlight. The occurrence mechanism is shown in following FIG. 2, as the light emitting angle of LED is generally about 120° and there is a certain gap between backlight LED structures 5, this results in a dark area W without light illuminating generated near the light incident surface of the light guide plate 2, and therefore bright spots or bright lines appear at the two sides of the display panel 6. Measures for solving bright spots or bright lines appearing on the display panel 6 at present are as following:
1. The length of the glue frame 4 is increased to shield the bright spots or bright lines at the two sides of the display panel, however, this goes against implementation of narrow frame design of LCD;
2. Reflective sheets are pasted at the two sides of the optical film 3 for shielding, however, this may add assembly parts, and the assembling may be complex.
3. The gap between the LED structure and the light guide plate 2 is increased to achieve light mixing distance, however, this may loss luminous efficacy.